1. Field of the Invention
This invention relates to a shroud for surrounding and restraining the movement of the flexible boot of a constant velocity universal joint of the plunging type, a type of universal joint that is widely used to join a propshaft in an automotive drive system to the differential.
2. Description of the Prior Art
Prior art automotive propshaft constant velocity universal joints of the plunging type typically include an outer joint member that is open at one end and has rectilinear grooves extending into the inside of the open end, an inner joint member that has an end that is inserted into the open end of the outer joint member and has grooves in the end that extends into the open end of the outer joint member, balls or other torque transmitting devices that extend between the grooves of the inner joint member and the grooves of the outer joint member to permit the transmission of torque from one of such joint members to the other, while permitting both angular and axial or plunging movement between the joint members, and a flexible boot in the form of a sleeve that has one end sealed to the inner joint member and the other end sealed to the outer joint member to retain grease in the region of the relatively moving parts of the joint and to prevent such relatively moving parts from being contaminated by water or dirt or other contaminants that it may encounter in normal service.
An automotive propshaft constant velocity universal joint of the foregoing type is subject to operation at relatively high rotational speeds, and such rotational speeds impart centrifugal force to the flexible boot which can cause the flexible boot to distort or balloon out in service, partly due to the mass of the boot and partly due to the mass of the grease that is contained within the boot, which also experiences such centrifugal forces. Such distortion of the boot can lead to a failure of the grease seal between the boot and the outer joint member, which inherently has a larger diameter than the inner joint member, and it permits the grease to be thrown away from the region of the relatively moving parts of the joint by virtue of the ballooning out of the boot and the centrifugal forces acting on the grease, thus, posing the danger of inadequate lubrication of the relatively moving parts of the joint during a time of high speed operation when proper lubrication is most important.
The problems arising from the distortion of the flexible boot of an automotive propshaft constant velocity universal joint have heretofore been dealt with by the use of a spun metal boot restraint that surrounds the portion of the boot that is sealed to the outer joint member to maintain the seal between the boot and the outer joint member and to restrain outward movement of the portion of the boot that is near the outer joint member, which is inherently the portion of the boot that has the largest diameter and is the most subject to distortion due to centrifugal force. Such a spun metal boot restraint is described in U.S. Pat. No. 3,822,570 (Fisher). A spun metal boot restraint of the type described in the aforesaid U.S. Pat. No. 3,822,570 is partially roll formed in place, and the rolling action that is needed to complete the forming of the restraint tends to cause twisting of the boot which can lead to premature boot failure. Also, once the spun metal boot restraint is in place, it cannot be removed without destruction of such boot restraint, and usually without destruction of the boot itself and, therefore, the servicing of a plunging constant velocity universal joint that utilizes such a spun metal boot restraint is difficult and expensive.